A176004 - OEIS

%I #7 Sep 04 2015 20:20:55

%S 1,1,2,3,3,4,2,7,6,11,8,9,12,15,20,15,18,20,18,22,25,27,32,32,29,30,

%T 27,28,41,44,46,46,55,56,51,52,52,55,60,60,69,70,68,66,77,82,85,86,88,

%U 93,86,93,98,102,103,102,100,103,100,108,120,117,112,115,128,132,141,140,140,145

%N (n-th prime > 3) minus (n-th semiprime).

%F a(n)=prime(n+2)-semiprime(n).

%t Module[{nn=80,sem,len},sem=Select[Range[3*nn],PrimeOmega[#]==2&];len= Min[nn,Length[sem]];#[[1]]-#[[2]]&/@Thread[{Take[Prime[Range[ 3,nn+2]], len],Take[sem,len]}]] (* _Harvey P. Dale_, Sep 04 2015 *)

%Y Cf. A168563.

%K nonn

%O 1,3

%A _Juri-Stepan Gerasimov_, Apr 11 2010, May 17 2010

%E a(6) corrected by _R. J. Mathar_, Apr 16 2010

%E Corrected and extended by _Harvey P. Dale_, Sep 04 2015